DOI: 10.1111/tgis.12709 RESEARCH ARTICLE Reference study of IFC software support: The GeoBIM benchmark 2019—Part I Francesca Noardo1 | Thomas Krijnen1 | Ken Arroyo Ohori1 | Filip Biljecki2,3 | Claire Ellul4 | Lars Harrie5 | Helen Eriksson5 | Lorenzo Polia6 | Nebras Salheb1 | Helga Tauscher7 | Jordi van Liempt1 | Hendrik Goerne8 | Dean Hintz9 | Tim Kaiser7 | Cristina Leoni10 | Artur Warchol11,12 | Jantien Stoter1 13D Geoinformation, Delft University of Technology, Delft, The Netherlands 2Department of Architecture, National University of Singapore, Singapore, Singapore 3Department of Real Estate, National University of Singapore, Singapore, Singapore 4Department of Civil, Environmental and Geomatic Engineering, University College London, London, UK 5Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden 6Architect, Turin, Italy 7Faculty of Spatial Information, Dresden University of Applied Sciences, Dresden, Germany 8GMX, Munich, Germany 9Safe Software, Surrey, Canada 10Department of Civil, Constructional and Environmental Engineering, Sapienza Univerisity of Rome, Rome, Italy 11Institute of Technical Engineering, PWSTE Bronislaw Markiewicz State University of Technology and Economics in Jaroslaw, Jaroslaw, Poland 12ProGea 4D sp. z.o.o., Kraków, Poland Correspondence Francesca Noardo, 3D Geoinformation, Abstract Delft University of Technology, Delft, The Industry Foundation Classes (IFC), the buildingSMART open Netherlands. Email: [email protected] standard for BIM, is underused with respect to its promising potential, since, according to the experience of practitioners Funding information European Union’s Horizon 2020 Research and researchers working with BIM, issues in the standard’s im- & Innovation Programme, Grant/Award plementation and use prevent its effective use. Nevertheless, Number: 677312; Marie Sklodowska-Curie, Grant/Award Number: 707404; International a systematic investigation of these issues has never been car- Society of Photogrammetry and Remote ried out, and there is thus insufficient evidence for tackling the Sensing (ISPRS) - Scientific Initiatives 2019 - GeoBIM benchmark project; European problems. The GeoBIM benchmark project is aimed at finding association for Spatial Data Research such evidence by involving external volunteers, reporting on (EuroSDR) - GeoBIM benchmark project This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2021 The Authors. Transactions in GIS published by John Wiley & Sons Ltd Transactions in GIS. 2021;25:805–841. wileyonlinelibrary.com/journal/tgis | 805 806 | NOARDO ET AL. various aspects of the behavior of tools (geometry, semantics, georeferencing, functionalities), analyzed and described in this article. Interestingly, different IFC software programs with the same standardized data sets yield inconsistent results, with few detectable common patterns, and significant issues are found in their support of the standard, probably due to the very high complexity of the standard data model. A companion ar- ticle (Part II) describes the results of the benchmark related to CityGML, the counterpart of IFC within geoinformation. KEYWORDS Industry Foundation Classes, building information models, open standards, software support, interoperability, GeoBIM 1 | INTRODUCTION In the architecture, engineering and construction (AEC) fields, as well as in other disciplines, interoperability is of increasing importance, in order to enable reuse and exchange of data and information, including in the strictly re- lated asset and facility management field. Furthermore, it is essential for reciprocal integration of different types of data. One of the current research topics is, for example, the integration of building information models (BIMs) with 3D city models, for supporting several use cases (e.g., building permits issuing, 3D cadastre, complex assets and facility management). International standards are conceived as a solution for fostering such interoperability. The most popular standard data models, considered for obtaining such integration, are usually the OGC CityGML for 3D city models and buildingSMART Industry Foundation Classes (IFC) for BIMs. However, although some building designers and professionals, supporting openBIM, are IFC enthusiasts, many others working with BIMs still seldom use IFC as a first choice for exchanging their models, and only export them to IFC when required explicitly by law, when trying to integrate with software from different vendors, or when no other solutions are available, as emerged from several personal communications. This often happens because they are aware of some limitations in the IFC format—as documented, for example, more than 10 years ago by Pazlar and Turk (2008), or in Barbini, Malacarne, Massari, Monizza, and Matt (2019)—although they might acknowledge its potential as an open exchange format. In practice, limited support for IFC might not been considered as a major issue, since some very widespread software, such as the Autodesk Revit format, is often used as a de facto standard for exchange of BIMs among de- signers, as well as for integrating the BIM with further systems (see, for example, Aksamija, 2018; Baik, Yaagoubi, & Boehm, 2015; Farid Mohajer & Aksamija, 2019; Kamari, Laustsen, Petersen, & Kirkegaard, 2018; Kensek, 2014; Lamartina & Sa, 2019; Lv, 2018; Papadopoulos, Sotelino, Martha, Nascimento, & Faria, 2017; Petersen, Bøving, Nielsen, & Purup, 2018), while the actual use of BIMs by authorities, is still limited for the moment, apart from for visualization. This solves the most immediate interoperability issues, even though the Revit format is a proprietary binary format, which hinders reusability in an open way and across time. A specific study of the limitations of IFC was part of the GeoBIM benchmark project (https://3d.bk.tudel ft.nl/ proje cts/geobi m-bench mark/, see Section 2) and is reported in this article. Within the project, the approach to the study of the support for the two standards involved in the GeoBIM integration (IFC and CityGML) was conceived NOARDO ET AL. | 807 in parallel, also with the aim of understanding whether one of the two offered more effective solutions that could possibly be borrowed by the other one in future developments. However, the final outcomes of the two different tasks are very specific for each standard and deserve to be presented and discussed separately, considering the specifics of each case. For these reasons, this article, which focuses on the results about the benchmark Task 1 (support for IFC), is written in tandem with Noardo et al. (2020c), which describes Task 3, covering the support for CityGML. In order to allow each article to be read on its own, the two articles share some information (i.e., Section 2 explaining the general context and motivation of the study; Section 3. 1 covering the initial part of the methodology about the entire GeoBIM benchmark set-up, and Section 3. 3 concerning some similarities in the methodology). One further article explores the parts of the project more directly related to the subject of inte- gration, namely, conversion procedures and useful tools to georeference IFC models Noardo, Harrie, et al. (2020). 2 | THE GeoBIM NEEDS AND THE IDEA BEHIND THIS STUDY Two kinds of 3D information systems have been developed, studied and used in recent times, revealing their potential in related fields: • 3D city models, which are used to represent city objects in three dimensions and advance previous 2D maps and other cartographic products, in order to support city analysis and management, city planning, navigation, and so on (e.g., Bartie, Reitsma, Kingham, & Mills, 2010; Biljecki, Stoter, Ledoux, Zlatanova, & Çoltekin, 2015; Egusquiza, Izkara, & Gandini, 2018; Jakubiec & Reinhart, 2013; Liang, Gong, Li, & Ibrahim, 2014; Kumar, Ledoux, Commandeur, & Stoter, 2017; Peters, Ledoux, & Biljecki, 2015; Nguyen & Pearce, 2012); • building information models, which are used in the architecture, engineering and construction fields to design and manage buildings, infrastructure and other construction works, and which also have features useful to project and asset management (e.g., Azhar, 2011; Haddock, 2018; Petri, Kubicki, Rezgui, Guerriero, & Li, 2017). Several international standards exist to govern the representation of the built environment in a shared manner, to foster interoperability and cross-border analysis and, consequently, actions, or to reuse tools, analysis methods and data themselves for research and, possibly, government. Some examples of international standards are: the European Directive for an infrastructure for spatial information in Europe (INSPIRE) (https://inspi re.ec.europa. eu), aimed at the representation of cross-border territories in Europe, for common environmental analysis; the Land and Infrastructure standard (LandInfra) (https://www.ogc.org/stand ards/landi nfra), by the Open Geospatial Consortium (OGC), aimed at land and civil engineering infrastructure facilities representation; and the green build- ing data model (gbXML) (https://www.gbxml.org), aimed at the representation of buildings for energy analysis. Nonetheless, the two dominant reference open standards for those two models are CityGML (citygmlwiki. org), by the OGC, focusing on urban-scale representation of the built environment, and the Industry Foundation Classes (ISO, 2013, https://techn